Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $87.85   8.328%   $95.1661   $95.17   $95.15   $95.20  
  Purchase #2 $227.99   13.814%   $259.4845   $259.48   $259.50   $259.50  
  Purchase #3 $189.54   12.204%   $212.6715   $212.67   $212.65   $212.70  
  Purchase #4 $54.98   6.229%   $58.4047   $58.40   $58.40   $58.40  
  Purchase #5 $232.68   9.150%   $253.9702   $253.97   $253.95   $254.00  
  Purchase #6 $187.43   12.216%   $210.3264   $210.33   $210.35   $210.30  
  Purchase #7 $227.47   12.230%   $255.2896   $255.29   $255.30   $255.30  
  7 purchase totals = $1,207.94       $1,345.3130   $1,345.31   $1,345.30   $1,345.40